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Ground in Bus-Duct

Ground in Bus-Duct

Ground in Bus-Duct

(OP)
A large 1 MVA, Delta-Wye transformer supplies a 480V, 3-Wire MCC via a bus-duct. The 20-foot length of bus-duct contains NO ground-bus, and no neutral, and the enclosure is NOT Listed for grounding.

The transformer secondary, and the Ground-Bar inside the MCC, are both connected to the grounding electrode system (i.e., underground ground grid, etc.).

Where in the NEC is this prohibited?

RE: Ground in Bus-Duct

See 250.4(A) if XO is grounded or 250.4(B) if XO is floated.
Don

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